1️⃣ Its speed will reduce
2️⃣ Its efficiency will improve
3️⃣ Its power factor will reduce
4️⃣ Its breakdown torque will reduce
✅ Answer (Detailed Solution Below)
✔️ Option 3: Its power factor will reduce
📖 Detailed Solution
🔹 The air gap increases the reluctance of the magnetic circuit.
🔹 When air gap is increased:
Reluctance increases.
Permeability decreases.
Magnetizing inductance decreases.
🔹 To maintain required flux, higher MMF is needed.
🔹 Higher MMF requires higher magnetizing current.
🔹 Magnetizing current is reactive.
🔹 Increase in reactive current lowers power factor.
🔹 Power factor becomes poor at all loads.
👉 Hence, increasing air gap reduces power factor.
⚙️ Effect of Increased Air Gap
✔️ Reluctance increases
✔️ Magnetizing current increases
✔️ Leakage flux increases
✔️ Power factor decreases
✔️ Torque decreases
✔️ Slip increases
📈 Performance Changes Due to Large Air Gap
🔹 Main flux decreases.
🔹 Mutual coupling reduces.
🔹 Breakdown torque reduces.
🔹 Speed decreases.
🔹 Efficiency reduces.
❌ Why Other Options are Incorrect
(1) Its Speed Will Reduce ❌
🔹 Speed reduces due to increased slip.
🔹 But this is a secondary effect, not the main electrical effect.
(2) Its Efficiency Will Improve ❌
🔹 Higher losses occur.
🔹 Efficiency decreases, not improves.
(4) Its Breakdown Torque Will Reduce ❌
🔹 Breakdown torque reduces.
🔹 But main direct effect is poor power factor.
📌 Additional Information
If Air Gap is Increased:
🔹 Reluctance ↑
🔹 MMF ↑
🔹 Magnetizing current ↑
🔹 Power factor ↓
🔹 Torque ↓
🔹 Speed ↓
📌 Key Exam Notes
⭐ Air gap ↑ → Im ↑
⭐ Air gap ↑ → PF ↓
⭐ Air gap ↑ → Torque ↓
⭐ Air gap ↑ → Slip ↑
📝 Final Summary
📍 Increasing the air gap increases magnetizing current, which lowers the power factor and degrades motor performance.
👉 Hence, Option 3 is Correct.